Mary and Joe are to throw three dice each. The score is the

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Mary and Joe are to throw three dice each. The score is the [#permalink]

23 Mar 2008, 13:23

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Mary and Joe are to throw three dice each. The score is the sum of points on all three dice. If Mary scores 10 in her attempt what is the probability that Joe will outscore Mary in his?

A - \frac{24}{64}
B - \frac{32}{64}
C - \frac{36}{64}
D - \frac{40}{64}
E - \frac{42}{64}
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Re: PS - Three dice... [#permalink]

23 Mar 2008, 14:11

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B

fast 30-sec approach:

1. the average score for three dices is: 3.5*3=10.5
2. one half of Joe possible scores will be less than 10 or equal, other half of Joe possible scores will be greater than 11 or equal.
3. B
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Re: PS - Three dice... [#permalink]

23 Mar 2008, 19:47

walker wrote:

My god, math killer Walker!

30-sec approach

from where does 3.5 derive?
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Re: PS - Three dice... [#permalink]

23 Mar 2008, 21:23

sondenso wrote:

from where does 3.5 derive?

1,2,3,4,5,6 ---> average=(1+2+3+4+5+6)/6=3.5
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Re: PS - Three dice... [#permalink] 23 Mar 2008, 21:23

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Mary and Joe are to throw three dice each. The score is the

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Mary and Joe are to throw three dice each. The score is the

Mary and Joe are to throw three dice each. The score is the

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